Problem: $ { {4} \times \left[\begin{array}{rr}{2} & {0} \\ {4} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{4}\times{2} & {4}\times{0} \\ {4}\times{4} & {4}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{8} & {0} \\ {16} & {4}\end{array}\right]}$